Do you want to shoot black powder or smokeless in it? Black powder is the easiest answer; have the bullet seated just short of the rifling and fill the case with powder so that it touches the base of the bullet. Be sure to use a drop tube and be sure to use a soft lube such as SPG.
For smokeless, loading data for 45-70 intended for trapdoor springfields are sure to be safe and those for mid strength guns probably also but stay away from those intended for the Ruger number 1
Just my thoughts at least. I shoot the caliber but almost always with black powder
cheers Doug